Spinocerebellar ataxia type 36

Spinocerebellar ataxia type 36 (SCA36), also known as Asidan or Costa da Morte ataxia, is a rare inherited neurodegenerative disorder caused by a GGCCTG hexanucleotide repeat expansion in the NOP56 gene on chromosome 20p13. The disease primarily affects the cerebellum and motor neurons, leading to progressive cerebellar ataxia characterized by gait unsteadiness, limb incoordination, and dysarthria (slurred speech). A distinctive feature of SCA36 is the involvement of motor neurons, which can produce tongue atrophy and fasciculations, giving it clinical overlap with motor neuron disease. Sensorineural hearing loss is another hallmark feature that distinguishes SCA36 from many other spinocerebellar ataxias. The condition was first described in families from the Galicia region of northwestern Spain (Costa da Morte) and subsequently identified in Japanese families, where it was termed Asidan (autosomal dominant spinocerebellar ataxia with axonal neuropathy). Symptoms typically begin in adulthood, usually between the ages of 35 and 60, and progress slowly over decades. Patients may also develop truncal ataxia, nystagmus, hyperreflexia in the upper limbs, and mild cognitive changes in later stages. Brain MRI typically shows cerebellar atrophy, particularly of the vermis. There is currently no cure or disease-modifying treatment for SCA36. Management is supportive and symptomatic, including physical therapy and rehabilitation to maintain mobility, speech therapy for dysarthria and swallowing difficulties, and hearing aids for sensorineural hearing loss. Occupational therapy and assistive devices may help maintain independence as the disease progresses. Genetic counseling is recommended for affected families given the autosomal dominant inheritance pattern.

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